WASHINGTON – The General Services Administration official who is emerging as a key figure in the inquires into a lavish 2010 agency conference in the Las Vegas area will invoke his Fifth Amendment right next week during a GOP-led House hearing on the issue, according to his lawyers.

However, the House oversight committee has issued a subpoena to require Jeffrey Neely -- the regional GSA administrator for the Western Region who was in charge of the 2010 conference -- to attend the hearing.

"The subpoena compels Mr. Neely to a appear before the committee on April 16," California Rep. Darrell Issa, chairman of the House Committee on Oversight and Government Reform, said in a letter to Neely's Washington attorney, Preston Burton.

Neely was invited Monday to testify before the committee’s “Addressing GSA’s Culture of Wasteful Spending” hearing, which will focus on the 2010 conference.

The 57-year-old Neely is one of six witnesses asked to appear but the only one who said he will not attend.

When Neely’s lawyer said his client would not attend, the subpoena was issued Thursday, according to the Issa letter.

Issa argues Neely might change his mind and answer some questions or be allowed to testify beyond the public’s eye, or perhaps receive immunity for his testimony.

The estimated cost for planning and holding the 2010 conference at the posh M Resort in Henderson, Nev., is now estimated at $830,000. The findings were made public last week in a GSA inspector general's report that has already resulted in a high-level shake up at the agency, with GSA chief Martha Johnson resigning and Neely being placed on administrative leave.

In addition, congressional sources told Fox News on Friday the GSA's inspector general is asking the Justice Department to probe the conference for possible criminal charges.

The inspector general investigation also uncovered such conference expenses as money spent on a clown suit, exercise bikes and a mind reader as well as hip-hop style videos in which agency employees are seen boasting about the yet-uncovered, excessive spending.

Further inspector general investigations, which have included interviews with GSA employees, uncovered a questionable employee-incentive program known as “Hats Off” and agency officials taking a week-long trip to Hawaii last year for a one-hour ribbon cutting ceremony for space leased by the federal government.

In addition, employees said bogus “Jackass” awards were created at conferences so there could be award ceremonies with taxpayer-funded meals. And in 2010, roughly 120 GSA and 20 regional mangers attended a networking event at the Palm Springs Riviera Resort and Spa suites in California.

The information was made public by the House Committee on Transportation and Infrastructure, which is also holding hearings next week on the agency’s questionable spending.

Susan Brita, the GSA’s deputy administrator and an Obama political appointee, emailed other agency officials in July 2011 saying the agency’s inspector general found “no substantive agenda” at the conference.

She also said that expenses for a clown suit, bicycles for a training exercise, tuxedos and a mind-reader “didn't lend themselves to the claim of a substantive conference.”

Brita suggested the agency should deal with the prospect of the news media latching onto the conference's nearly $1 million cost.

If the story “were to hit the press, what would public reaction be?” Britta wrote. “What would congressional reaction be?”

Last year, Brita questioned why Neely had received only a disciplinary letter.

Britta called Neely a “seasoned” administrator “who is expected to display the highest standards of common sense and prudent financial management. He did neither.”

She called the disciplinary letter “not even a slap on the wrist.”.

In other emails, Administrator Johnson discusses the performance and bonuses for Neely. In one email, Johnson defends giving him a bonus, saying he was an acting regional administrator “for forever and a day.”

Multiple emails between her and Bob Peck, the GSA’s public buildings administrator, refer to Neely as a “Steve Jobs” type, “someone who is very creative and does good work ... but doesn't fit conveniently into the standard human resources boxes.”

In one email, Johnson describes Peck as having a “problematic personality” and refers to his behavior with an unnamed congressman when both were in California.